Historically, the design, production, manufacture, and delivery of residential dwellings (i.e., homes) has marginally evolved over time. One of the more familiar paths has been design and construction of “site-built” homes. Site-built homes are extremely popular and are the mainstay of home building.
However, site-built homes necessitate many inefficiencies in the design and construction process to complete and, as they become more complex, they are disproportionately expensive, time-consuming and environmentally inefficient to deliver. For instance, steps to complete the construction of such a home require the organization and sequencing of unrelated labor and material demands to coalesce around a construction system and configuration largely unfamiliar to the work force. These components need to be ordered, shipped, organized, and sequenced through a critical path of construction. The shell for instance cannot proceed until the entire excavation, foundation and sill plates are complete, and the interior finishing cannot start until all the interior mechanical systems are fully installed. And so on and so on. These various steps are necessarily timed in a linear sequence and cannot be “fast tracked” without significant premiums and risk of error. The process is time consuming, variable in quality because of the varying work conditions and labor over the job, subject to weather and labor delays, and highly unpredictable in terms of costs and time. The job conditions are also environmentally taxing because of the extensive transportation of workers and machinery to and from a remote job sight, construction material waste on site, inconsistent waste material disposal, etc. . . . Accordingly, site-built custom homes can take as long as two or three years (or even longer) before the home is ready for occupancy and over that period of development contribute significant greenhouse gasses (GHG) and material waste into the environment.
Beginning in the 1950's, however, a type of housing construction in which the home was largely assembled elsewhere and then transported to the building site began to emerge. Such home building process was known as manufactured, or “pre-fabricated”, housing. Pre-fabricated homes can either be constructed through a panelized means of construction (“pre-fab panelized”) or a modular means of construction (“pre-fab modular”) but the means and methods of construction remained largely conventional.
Prefab modular is an interior finished floor, wall and ceiling assembly making a module “box” that is designed to be stacked or set next to another, joined with a site installed exterior skin to create a living space. Because it is fabricated in its final room dimensions, and conceived to be paired with other modules, the interior size and configurations are limited to road and bridge clearance on the transportation route from the factory to the site. This results in a system that is very rigid dimensionally, inefficient for transportation and shipping, fully integrated but limited in architectural expression and by complexity of site conditions.
Prefab panelized is a panel based system that joins precut panels to make an enclosure. Usually the panels are only a component of the structure and need to be combined with other site assembled structural systems to stand. The product most often does not integrate multiple trades in the manufacturing process. Because the system is panelized it ships very efficiently but it requires the same trades and basically the same time frame that a site-built custom home would take to fully finish. It is best applied as a single trade, structural and exterior skin solution with limited expectations for a factory finished interior. Because the panels are structurally limited and generally dependant on secondary systems such as column frames for joining they are also limited in dimension and result in great complexity in creating a weatherproof, code compliant exteriors.
As a result both panelized and modular means of construction have had limited applicability to complex or custom projects. Their application has most widely been applied to ubiquitous structures, temporary building where speed and low cost, but not quality, customization or durability, are primary. Because of this demand they are generally made of materials that are inexpensive and that allow for quick and easy assembly of the structure.
While pre-fabricated homes require much less site labor, they are targeted to be cheaper to build and buy as compared to the conventional site-built homes, and, as such, pre-fabricated homes are not widely applicable to the custom housing marketplace. Indeed, pre-fabricated homes are generally considered to be very basic “box” style buildings with little ability to vary character within a system. Within the parameters of a given methodology or system, the pre-fabricated homes tend to have very limited design options that significantly alter both the form and character of a product. Building sites that are most suitable for pre-fabricated homes tend to be limited to those that are easily accessible and with simple, flat or very gentle topography. In other words, home sites that can only be accessed via narrow roads, gates, under low overpasses, or that are on sloped sites are very challenged for the current methodologies for pre-fabricated homes.
Accordingly, it is clear that while existing technology in pre-fabricated modular or panelized homes do have certain advantages, there are still also many unsolved problems and execution difficulties associated with such homes. Thus, if pre-fabricated homes were able to have significant improvement of quality and features, these homes would have greater acceptance by a growing segment of the residential marketplace and realize a significant efficiency both economically and environmentally.